This invention relates to polysaccharide derivatives and polysaccharide graft polymers which contain organosiloxane substituents. These compositions are prepared by reacting a polysaccharide with a difunctional reagent which contains a siloxane group and a group which will react with a polysaccharide. The polysaccharide-reactive group of the reagent forms an ether or ester linkage with the polysaccharide, thereby attaching a reactive siloxane group to the polysaccharide. These organosiloxane-containing polysaccharides are employed in glass fiber size compositions to improve size adhesion to glass fibers, in paper-making to increase dry strength in paper, and the like.
Other silicon-containing polysaccharide compositions are known. In one class of such compositions, the silane group is bonded directly to a hydroxyl group of the polysaccharide. The compositions are prepared by first hydrolyzing the siloxane functionality of the reagent to the corresponding silanol, and then reacting the silanol with starch. One member of this class of starch organosilanes forms more viscous aqueous dispersions than unmodified starches and is useful for the hydrophobation of cellulosic materials, and as binders for mineral fibers, textile additives, paper sizes and plastic fillers. See U.S. Pat. No. 4,540,777. Other starch organosilanes are hydrophobic and free-flowing. See U.S. Pat. No. 3,071,492. Such compositions are not useful in applications taught herein which require the presence on the polysaccharide of siloxane substituent(s) that are available for further reaction.
Silicone-containing amylose films have been prepared by contacting the surface of a preformed amylose film with organo-silicon halides. See U.S. Pat. No. 3,398,015. The silicon is bonded directly to the amylose, and the amylose-silicone films are reported to exhibit hydrophobic properties.
Organosiloxane-containing polysaccharide derivatives wherein the siloxane group is available as a reactive group are taught in commonly assigned patent, U.S. Pat. No. 4,839,449, to Billmers, et al., issued June 13, 1989. However, unlike the compositions disclosed herein, the derivatives disclosed in that application require a two step, dual reagent process for preparation, and the products of that process are limited to divalent aromatic group-containing, nitrogen-containing derivatives. Thus, the derivatives and polymers disclosed herein offer advantages of greater flexibility, process efficiency, reagent availability and reduced costs over known organosiloxane-containing polysaccharides.
The present invention also relates to a glass fiber forming size composition, comprising the organosiloxane-containing polysaccharides of this invention; and to a method for preparing glass fibers, and, in particular, to the application of the forming size to continuous filament glass fiber strands.
In glass fiber production, molten glass flows or is pulled through tiny orifices or tips in a heated platinum bushing. The individual glass filaments are passed through a sizing bath, grouped into a strand, and then wound on a rapidly rotating forming tube. The size is applied to the filaments in order to bind them together, maintain the integrity of the strand during winding and unwinding, and facilitate eventual processing. The strand on the forming tube is thereafter placed in an oven to dry or is allowed to air dry to reduce the moisture content of the strand.
Many different compositions have been used as glass forming sizes. Typically, the sizes have comprised aqueous dispersions of various modified and unmodified starches and oils. Numerous patents are directed to starch or other polysaccharide-containing glass fiber size compositions. Illustrative patents include U.S. Pat. Nos. 3,227,192; 3,167,468; 3,481,771; 3,664,855; 3,793,065; 3,928,666; and 4,168,345. Typical polysaccharide-containing glass fiber forming size compositions which are useful herein are disclosed in U.S. Pat. Nos. 3,615,311; 4,166,872; 4,780,339; and 4,259,190, the disclosures of which are hereby incorporated by reference.
In addition, U.S. Pat. No. 4,500,600 (issued Feb. 19, 1985 to Wong et al.) discloses glass fibers coated with a size containing gamma-aminopropyltriethoxysilane and a selected alkoxysilane, and a method for making such fibers. Unlike the sizes disclosed herein, the Wong et al. sizes do not bond a polysaccharide to the glass, and the fibers made with the Wong et al. size are designed for use in reinforced plastics. They are not suited for applications requiring significant adhesion of the size to the glass fiber.
There remains a need for new polysaccharide derivatives, especially derivatives containing silane groups which are useful in glass forming sizes and which display improved adhesion to glass.